The low thermal expansion member 130 is a member made of a material having a low thermal expansion coefficient. In this embodiment, the low thermal expansion member 130 is made of SUS430. The low thermal expansion member 130 may be made of Kovar, or the like. In the low thermal expansion member 130, a fitting portion 131, and plural fuel gas passages 132 are formed. The fitting portion 131 is formed so as to have a recess portion. The plural fuel gas passages 132 are formed so as to penetrate a bottom surface of the fitting portion 131.
However, hydrogen separation metal has a high thermal expansion coefficient and a high hydrogen expansion coefficient, whereas ceramics has a low coefficient thermal expansion and a low hydrogen expansion coefficient. Therefore, compression stress is applied to the hydrogen separation metal, and tensile stress is applied to the ceramics due to heat that is generated when the fuel cell is operated. Accordingly, there is a problem that the ceramics is separated from the hydrogen separation metal at an interface therebetween due to the stress.
When the hydrogen separation metal and the ceramics are made thin, hydrogen-permeability can be increased, and performance of the fuel cell can be improved. However, when the hydrogen separation metal and the ceramics are made thin, there is the problem that the ceramics is likely to be broken or separated from the hydrogen separation metal.